For example, in the lens of glasses and the like, lens processing is necessary to adjust the shape of the lens to fit the shape of the frame, design of the frame, and the like, and therefore machining (known as edging) such as grooving or chamfering with a grindstone is executed. To execute the machining described above for the lens, a so-called lens-grinding machine is used and the shape of the lens can be altered to fit the shape of the frame of the glasses by mounting the lens supplied by the lens maker in the grinding machine and grinding the periphery with a grindstone.
The lens grinding machine, for example, is structured in a manner such that it contains a grinding chamber to process the lens, sandwiches the lens between a pair of clamp arms extending from drive units disposed on both sides of the grinding chamber, and grinds the periphery of the lens with the grindstone as the clamp arms rotate. A holding jig is attached to the tip of one of the clamp arms, the tip of the other clamp arm is equipped with an elastic material such as rubber and becomes the lens holder, and the lens to be processed is fixed by being sandwiched between these two clamp arms.
At this time, when the holding jig directly contacts the surface of the lens to be processed, since there are the worries that, for example, the surface of the lens to be processed will be scratched and that accurate processing cannot be performed because of possibilities such as the holding jig slipping and causing axial misalignment, adhesive tape is interposed between the holding jig and the lens to be processed when the lens to be processed is sandwiched by the holding jig.
In recent years, various surface coatings are administered to the lens used for glasses and the like, creating the problem that common adhesive tape cannot achieve sufficient adhesion. For example, in a lens with antifouling coating that makes dirt less likely to stick to the surface, the antifouling layer (water repellent coating) is formed by coating the surface of the lens with water repellent material such as a fluorine-containing silane compound. This water repellent coating does not only make dirt less likely to stick, but also has low hydrophilic properties in relation to the adhesive agent of the adhesive tape, and notably decreases the friction coefficient. Accordingly, with common adhesive tape, there is the problem that a large amount of holding power cannot be achieved and precise processing is impossible because of axial misalignment.
Considering the condition described above, various improvements have been attempted for the fixing of the lens with adhesive tape (see, e.g., Patent Document 1 (Japanese Patent Application Publication No. 2004-122302), Patent Document 2 (Japanese Patent Application Publication No. 2004-249454)). Specifically, in the invention described in Patent Document 1, a transparent adhesive sheet, that contains a surface having hydrophilic properties more favorable than the surface of the lens in relation to the adhesive agent and provided with an adhesive layer on the side of the lens, is affixed to the lens surface to attach the holding jig on the adhesive sheet via a double sided adhesive tape.
On the other hand, the invention described in patent document 2, for example, proposes a method for distinguishing adhesive tape having superior adhesive strength in relation to the antifouling layer formed mainly of a fluorine-containing silane compound, and adhesive strength in relation to the antifouling layer is assured to prevent axial misalignment by selecting the adhesive strength greater than or equal to a prescribed value in a case where a polyethylene terephthalate plate serving as a test plate that receives surface processing with a fluorinated silicone release agent I used.
However, as shown in the invention of Patent Document 1, in the method that simultaneously uses the adhesive sheet and the double sided adhesive tape, not only is the process of affixing the sheet and tape troublesome, but also there are unsatisfactory costs because an adhesive sheet with a large surface area is necessary. Furthermore, because of the water repellent coating, it is difficult to completely eliminate axial misalignment because sufficient holding power cannot be reliably achieved even with the large surface area of the adhesive sheet.
On the other hand, as shown in the invention of Patent Document 2, in a case where focus is placed on the adhesive strength of the adhesive tape, the use of the adhesive tape having high adhesive strength in relation to the antifouling layer leads to the prevention of axial misalignment, but where merely using the adhesive tape having high adhesive strength, the amount of strength required to peel off the adhesive tape is too great, creating the possibility that the antifouling layer or the like is also removed at a time when the adhesive tape is removed after processing. Therefore formation of a supplemental piece for protecting the surface coating becomes necessary, leading to a higher cost of the adhesive tape.